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Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
JPS Conference Proceedings (Internet), 45, p.011174_1 - 011174_10, 2026/06
A 30 MW continuous wave proton linac is devised by the Japan Atomic Energy Agency (JAEA) for the use of Accelerator Driven Subcritical System (ADS) technology. The efficiency of the accelerator is crucial for the realization of ADS in terms of minor actinides management. Therefore, it is necessary to assess the overall efficiency of the different components to ensure the accelerator's feasibility. This study estimated the power required to operate RF cavities, considering effects such as beam loading and microphonics. Additionally, the contribution of cryogenics was considered by calculating the heat load generated by the cryomodules, as well as the power consumption of auxiliary systems such as magnets. In this analysis, we will present the efficiency estimations of the JAEA-ADS linac, as well as the methodology used to obtain the results.
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
JPS Conference Proceedings (Internet), 45, p.011171_1 - 011171_7, 2026/06
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
JPS Conference Proceedings (Internet), 45, p.011173_1 - 011173_7, 2026/06
The Japan Atomic Energy Agency (JAEA) is carrying out research and development on an Accelerator Driven Subcritical System (ADS) for nuclear transmutation. The JAEA-ADS consists of a CW superconducting proton linac of 30 MW coupling with a subcritical core reactor. The linac will accelerate a 20-mA proton beam to a final energy of 1.5 GeV, starting with a Normal Conducting section up to 2.5 MeV, and followed by a Superconducting part. More than 300 LLRF systems will control longitudinal parameters of the RF structures that compose the linac. In addition to ensuring stability on RF settings for efficient linac performance, the JAEA-ADS LLRF system will also enable fault-tolerance compensations to increase the availability of the linac, which is a major challenge for ADS operation. In this work, we will discuss the necessity of the ADS LLRF and present a proposed model that satisfies these demands.
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
Proceedings of 22nd International Conference on RF Superconductivity (SRF2025) (Internet), p.691 - 694, 2026/04
Japan Atomic Energy Agency (JAEA) has been proposing an accelerator-driven nuclear transmutation system (ADS) as a future nuclear system to efficiently reduce high-level radioactive waste generated in nuclear power plants. As the first step toward the full-scale CW proton linac for the JAEA-ADS, we are currently prototyping a low-beta (around 0.2) single-spoke cavity. Since there is no experience in manufacturing superconducting spoke cavities in Japan, prototyping and performance evaluation of the cavity are essential to ensure the feasibility of the JAEA-ADS. The actual cavity fabrication started in 2020, and the cavity assembly by electron beam welding was finally completed in fiscal year 2024. In this assembly, the target resonance frequency of 324 MHz was achieved by trimming the ends of the cavity parts several times before the final welding. In the final welding, smooth weld beads were obtained by combining circular-correction and end-thinning for the cavity parts to be welded. The fabrication of the prototype spoke cavity is presented.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio; Miyamoto, Ryoichi*; Milas, N.*; Eshraqi, M.*
Proceedings of 22nd International Conference on RF Superconductivity (SRF2025) (Internet), p.58 - 62, 2026/04
The European Spallation Source (ESS) superconducting proton linac is currently undergoing commissioning. During the initial operation phase, the final beam energy will be about 800 MeV, reaching a 2 MW power. High reliability and availability are crucial for the success of the ESS science programs and thus operations will be maintained even with failures of main linac components such as cavities and quadrupoles, as long as ~50 percent of the intended power can be achieved. To this end, we developed beam optics strategies to address failures in the cavities of the superconducting linac. Due to the constraints in the RF cavity amplitudes, we implemented a modified version of standard cavity compensation techniques. The results indicated that this strategy enables beam recovery that meets the beam quality specifications, thereby enhancing the availability of the ESS linac.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio; Pla
ais, A.*; Bouly, F.*
Proceedings of 22nd International Conference on RF Superconductivity (SRF2025) (Internet), p.316 - 320, 2026/04
High-intensity accelerators, particularly Accelerator-Driven Systems (ADS), require high availability and reliability for proper operation. For superconducting linear accelerators, the ability to continue operating even when one of the RF cavities fails is key to achieving the required availability, known as cavity compensation. Beam dynamics studies of the JAEA-ADS linear accelerator have demonstrated the possibility of operating with multiple RF cavities disabled with acceptable beam quality. Several other superconducting linear accelerator laboratories have adopted similar methods and developed their procedures. Among these efforts, the LightWin tool has proven to be an effective tool for automatically and systematically identifying compensation settings for each cavity failure in any linear accelerator. This software has been successfully utilized on the MINERVA linac, as well as on the high-energy part of the JAEA-ADS linac. It has currently been tested and improved to ease SPIRAL2 operation. This work presents an analysis of cavity compensation in the JAEA-ADS superconducting linear accelerator using the LightWin tool and compares the results with previous studies.
Morohashi, Yuko; Yamada, Ippei; Kobayashi, Fuminori; Tamura, Jun; Miyao, Tomoaki*; Moriya, Katsuhiro; Kamiya, Junichiro
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.508 - 511, 2026/03
no abstracts in English
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.130 - 134, 2026/03
Accelerator-Driven Systems (ADS) represent an efficient solution to the challenge of nuclear waste disposal. Therefore, the Japan Atomic Energy Agency (JAEA) is designing a 30-MW proton linac as a key element of its proposal for the use of ADS technology. A key feature of ADS accelerators is their extremely high availability and reliability that is required to avoid thermal stress on reactor structures. To this end, JAEA-ADS adopted a combined strategy of hot standby in the front part of the linac and standby element compensation as a fast and efficient way to reduce the downtime due to an element failure. The JAEA-ADS injector is mainly composed of a normal conducting section and ends with the first section of superconducting cavities (Half Wave Resonator). This paper presents the details of the optics design of the JAEA-ADS injector and the results of beam dynamics simulations.
Kondo, Yasuhiro; Chimura, Motoki; Cicek, E.*; Fukui, Yuji*; Futatsukawa, Kenta*; Fuwa, Yasuhiro; Goto, Rikuto*; Hirano, Koichiro; Ishikawa, Masaki*; Ito, Takashi; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.124 - 129, 2026/03
Various upgrade plans of the J-PARC linac are underway, and repetition-rate doubling project is one of the most important part. Currently, the linac supplies a 400~MeV H
ion beam to the 3~GeV synchrotron (RCS) at a repetition rate of 25~Hz. However, to deliver the beam to both RCS and proton-beam irradiation facility under planning, it is necessary to raise the repetition rate from 25~Hz to 50~Hz. Prior to construction of the beamline to the irradiation facility, we conducted a verification of the 50~Hz operation of all the linac apparatus simultaneously within the current operational limits in May 2025. And also, the verification of the 50~Hz operation of the particle counter system, which is one of the most important safety device of the J-PARC accelerator, was conducted. As a result, any significant problems were not found out, and it is now ready for the upcoming 50~Hz-beam acceleration demonstration. This paper describes this details of the demonstration of the 50~Hz operation, without beam acceleration, of the J-PARC linac.
Liu, Y.*; Otani, Masashi*; Miyao, Tomoaki*; Nakazawa, Yuga*; Shibata, Takanori*; Nammo, Kesao*; Fang, Z.*; Futatsukawa, Kenta*; Fukui, Yuji*; Mizobata, Satoshi*; et al.
Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.855 - 857, 2025/11
Asamori, Koichi; Sueoka, Shigeru; Komatsu, Tetsuya; Ogata, Manabu; Uchida, Mao; Nishiyama, Nariaki; Tanaka, Kiriha; Kobayashi, Tomoharu; Mitsuguchi, Takehiro; Murakami, Osamu; et al.
JAEA-Review 2025-035, 29 Pages, 2025/10
JAEA-Review-2025-035.pdf:1.12MB
This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2025. The objectives and contents of this research are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.
Morita, Mana*; Kiyama, Tamotsu*; Fukuda, Daisuke*; Aoyagi, Kazuhei; Tamura, Tomonori; Yagi, Keisuke*; Kodama, Junichi*
Shigen, Sozai Koenshu (Internet), 12(2), 5 Pages, 2025/09
no abstracts in English
Asakawa, Jun; Kimura, Yasuhisa; Hirano, Hiroshi*; Kitamura, Akihiro
Hoken Butsuri (Internet), 60(1), p.63 - 73, 2025/04
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Maekawa, Fujio; Meigo, Shinichiro
Proceedings of 21st Annual Meeting of Particle Accelerator Society of Japan (Internet), p.205 - 209, 2024/10
The Japan Atomic Energy Agency (JAEA) designs a 30-MW CW proton linear accelerator (linac) as a key component for the accelerator-driven subcritical system (ADS) project, aimed at nuclear waste management. The low energy beam transport (LEBT) in JAEA-ADS uses charge neutralization to minimize space-charge effects, which are the primary cause of beam loss in high-power accelerators. During commissioning and power ramp-up, precise control of the duty cycle is required for safety and machine protection; thus, a chopper system will be installed to manage the beam power. The chopper is located at the LEBT, to facilitate the disposal of the excess beam power, but its operation will affect the charge neutralization producing beam transients that could lead to beam loss. To shed light on this, we created a beam optics model for the chopper using an analytic approach to determine the required characteristics like voltage and dimensions, which was confirmed through TraceWin simulations. Subsequently, we analyzed the chopper's impact on space-charge compensation to evaluate the beam transients in the LEBT. This study reports the design of the chopper and its effects on beam performance for the JAEA-ADS LEBT.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Maekawa, Fujio; Meigo, Shinichiro
Proceedings of 32nd Linear Accelerator Conference (LINAC 2024) (Internet), p.488 - 491, 2024/10
The Japan Atomic Energy Agency (JAEA) is designing a 30-MW CW proton linear accelerator (linac) for nuclear waste transmutation. Space-charge is the primary challenge in achieving low losses and high beam quality for high-power accelerators, especially at low energy levels where space-charge forces are greater. To counteract the space-charge effects, the low-energy beam transport (LEBT) uses a magnetostatic design to enable the neutralization of the beam charge, the so-called space charge compensation. The neutralization is an accumulation process that reaches a charge balance between the main beam and the opposite ionized particles. However, this equilibrium is destroyed by the chopper system used during beam ramping. During those transient regimes, the beam optics conditions are not optimal for the beam, producing considerable degradation that can end in serious damage to the accelerator. Thus, analysis of beam behavior at these periods is essential to develop a robust design and an efficient operation of the JAEA-ADS linac. This study presents the beam dynamics of neutralization build-up and chopper operation for the JAEA-ADS LEBT.
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
Proceedings of 32nd Linear Accelerator Conference (LINAC 2024) (Internet), p.496 - 498, 2024/10
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
Journal of Physics; Conference Series, 2687(5), p.052008_1 - 052008_6, 2024/01
Times Cited Count：0 Percentile：0.00(Physics, Atomic, Molecular & Chemical)
Be ground-state molecular structure using Be(
)
He triple differential reaction cross-section measurementsLi, P. J.*; Beaumel, D.*; Lee, J.*; Assi
, M.*; Chen, S.*; Franchoo, S.*; Gibelin, J.*; Hammache, F.*; Harada, T.*; Kanada-En'yo, Yoshiko*; et al.
Physical Review Letters, 131(21), p.212501_1 - 212501_7, 2023/11
Times Cited Count：36 Percentile：94.69(Physics, Multidisciplinary)The cluster structure of the neutron-rich isotope Be has been probed via the () reaction. The triple differential cross-section was extracted and compared to distorted-wave impulse approximation reaction calculations performed in a microscopic framework using the Tohsaki-Horiuchi-Schuck-R
pke wave function and the wave function deduced from Antisymmetrized Molecular Dynamics calculations. The remarkable agreement between calculated and measured cross-sections in both shape and magnitude validates the description of the Be ground-state as a rather compact nuclear molecule.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Maekawa, Fujio; Meigo, Shinichiro
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.545 - 549, 2023/11
The Japan Atomic Energy Agency (JAEA) is proposing a 30-MW proton linear accelerator (linac) for the application of accelerator-driven subcritical system (ADS) technology to achieve nuclear waste transmutation. A major challenge for the JAEA-ADS linac is the efficient transport of a 35 keV proton beam from the ion source to the radio-frequency quadrupole. In order to achieve this goal, we have optimized a magnetostatic low energy beam transport (LEBT) consisting of two solenoids to reduce the transmission of high-charge ions generated by the source and minimize the growth of proton emittance, while taking into account various space-charge compensation scenarios. In this report, we present the optical design and discuss the multiparticle tracking results of the JAEA-ADS LEBT.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Maekawa, Fujio; Meigo, Shinichiro
Proceedings of 14th International Particle Accelerator Conference (IPAC 23) (Internet), p.1591 - 1593, 2023/09
The Japan Atomic Energy Agency (JAEA) is designing a 30 MW continuous wave (cw) superconducting proton linear accelerator (linac) for the Accelerator Driven System (ADS) proposal. The JAEA-ADS linacs ion source must provide a proton beam over 20 mA with an energy of 35 keV and a normalized rms emittance of less than 0.1 
mm mrad. As the extraction system determines the beam properties and quality, systematic optimizations on the geometry and input values of the extraction system design were conducted using the AXCEL-INP 2-D simulation program to satisfy the goal requirements. This work describes the extraction system design and reports the beam dynamics results of the first study for the proton source of the JAEA-ADS linac.
